Integrated production of FCC-produced C3 and cumene

ABSTRACT

Processing schemes and arrangements are provided for obtaining propylene and propane via the catalytic cracking of a heavy hydrocarbon feedstock and converting the propylene into cumene without separating the propane from the propane/propylene feed stream. The disclosed processing schemes and arrangements advantageously eliminate any separation of propylene from propane produced by a FCC process prior to using the combined propane/propane stream as a feed for a cumene alkylation process. A bottoms stream from the cumene column of the cumene alkylation process can be used and an absorption solvent in the FCC process thereby eliminating the need for a transalkylation reactor and a DIPB/TIPB column.

TECHNICAL FIELD

This disclosure relates generally to hydrocarbon processing. Morespecifically, this disclosure relates to the initial processing ofhydrocarbon-containing materials into an intermediate stream includingpropylene and propane produced by the cracking of a heavy hydrocarbonfeedstock. This disclosure also relates to the subsequent use of saidintermediate stream in the making of valuable aromatics, such as cumene.

BACKGROUND OF THE RELATED ART

Light olefins serve as feed materials for the production of numerouschemicals. Light olefins have traditionally been produced through theprocesses of steam or catalytic cracking of hydrocarbons such as derivedfrom petroleum sources. Fluidized catalytic cracking (FCC) of heavyhydrocarbon streams is commonly carried out by contacting relativelyhigh boiling hydrocarbons with a catalyst composed of finely divided orparticulate solid material. The catalyst is transported in a fluid-likemanner by transmitting a gas or vapor through the catalyst at sufficientvelocity to produce a desired regime of fluid transport. Contact of theoil with the fluidized catalyst results in the cracking reaction.

FCC processing is more fully described in U.S. Pat. Nos. 5,360,533,5,584,985, 5,858,206 and 6,843,906. Specific details of the variouscontact zones, regeneration zones, and stripping zones along witharrangements for conveying the catalyst between the various zones arewell known to those skilled in the art.

The FCC reactor serves to crack gas oil or heavier feeds into a broadrange of products. Cracked vapors from an FCC unit enter a separationzone, typically in the form of a main column, that provides a gasstream, a gasoline cut, light cycle oil (LCO), heavy cycle oil (HCO) andclarified oil (CO) components. The gas stream may include hydrogen, C₁and C₂ hydrocarbons, and liquefied petroleum gas (“LPG”), i.e., C₃ andC₄ hydrocarbons.

There is an increasing need for light olefins such as propylene for theproduction of polypropylene, isopropyl benzene (cumene) and the like asopposed to heavier olefins. Research efforts have led to the developmentof an FCC process that produces or results in greater relative yields oflight olefins, i.e., propylene. Such processing is more fully describedin U.S. Pat. No. 6,538,169.

Cumene is an important intermediate compound for the production ofphenol, acetone, alpha-methylstyrene and acetophenone. A conventionalFCC process produces a combined propane/propylene stream. Thepropane/propylene stream is typically run through a splitter ordistillation column to separate the propylene from the propane. Theoperation of such a splitter is energy intensive in addition toconstruction and maintenance costs.

In view of the increasing need and demand for light olefins such aspropylene and the use thereof in useful aromatics such as cumene, thereis a need and a demand for improved processing and arrangements for theseparation and recovery of light olefins from such FCC process effluentand the efficient conversion of those olefins into useful aromaticintermediates.

SUMMARY OF THE INVENTION

An integrated process is disclosed for (i) catalytically cracking (FCC)a heavy hydrocarbon feedstock, (ii) obtaining a combinedpropane/propylene stream, and (iii) reacting the propylene of thecombined propane/propylene stream with benzene to produce a cumeneproduct stream. The integrated process comprises contacting a heavyhydrocarbon feedstock with a hydrocarbon cracking catalyst in afluidized reactor zone to produce a hydrocarbon effluent stream thatincludes propane and propylene. The process then further comprisesseparating the combined propane/propylene stream from the hydrocarboneffluent stream, passing the combined propane/propylene stream to analkylation reactor; and reacting at least some of the propylene of thecombined propane/propylene stream with benzene in the alkylation reactorto produce cumene.

By linking the FCC process directly to the cumene alkylation process,substantial capital and energy costs savings are achieved. First, theneed for a propane/propylene splitter column is eliminated as propane isinert to the cumene alkylation process and does not hinder the processin any appreciable way. Second, along with the energy savings achievedby eliminating the propane/propylene splitter, additional energy savingsare achieved by linking the intercooler used to cool the alkylationreactor to one of the splitter columns of the FCC process.

Another integration option involves eliminating the transalkylationsection and the diisopropyl benzene (DIPB) column from the cumenealkylation process, and sending the cumene column bottoms to primaryabsorber in the FCC process for use as solvent. The cumene bottomsstream is used to supplement the debutanized gasoline recycle, which isused as a primary absorber solvent. If all of the propylene generated inthe FCC process is used in the cumene alkylation, the cumene columnbottoms would reduce the required debutanized gasoline recycle by15-20%. The DIPB and triisopropyl benzene (TIPB) would ultimately end upas a high octane component in the gasoline product.

Finally, because the TIPB may be slightly too heavy for the gasolinepool, another alternative is to send the cumene column bottoms to theFCC main column, where the heavier species in this stream would beremoved in a heavier fraction such as the heavy naphtha draw. Thelighter species in this stream will still act to reduce the requireddebutanized gasoline recycle, as they will exit in the unstabilizedgasoline that is recovered from the main column overhead.

Thus, in accordance with this disclosure, the propane is preferably notstripped from the combined propane/propylene stream prior to thecombined propane/propylene stream entering the alkylation reactor. Thepropane content of the combined propane/propylene stream may range up toabout 30 wt %.

The hydrocarbon effluent generated in the FCC process passes through aseparation zone to form a separator liquid stream and a separator vaporstream. C₂− hydrocarbon materials are stripped from the separator liquidstream in a stripper column to form a C₃+ hydrocarbon process streamsubstantially free of C₂− hydrocarbons. This stripper column may beadvantageously heated with heat generated in the alkylation reactor.Thus, heat may be transferred from the intercooler used to cool thecumene alkylation reactor to the stripper column to lessen the coolingduty of the intercooler and therefore, reducing cooling water costs.

The bottoms from the C₂− stripper is then passed through a debutanizerwhich generates a bottoms debutanized gasoline product stream, part ofwhich can be used as absorber solvent, and an overhead C₃-C₄ stream. Theoverhead C₃-C₄ stream is then passed through a caustic treatment zone toremove hydrogen sulfide, an extraction unit to catalytically oxidizemercaptans present to disulfides via a caustic wash, and a C₃/C₄splitter to remove mixed C₄ products to provide a C₃ overhead stream,which becomes the propane/propylene stream used for cumene alkylation.

The propane/propylene stream may be passed through a dryer, aregenerative COS treater to remove COS, and an arsine and/or phosphinetreater to effect removal of trace amounts of arsine and/or phosphineprior to sending the propane/propylene stream to the cumene alkylationunit.

An integrated system is disclosed for (i) catalytically cracking ahydrocarbon feedstock, (ii) obtaining selected hydrocarbon fractionsincluding a combined propane/propylene stream and (iii) reacting thepropylene of the combined propane/propylene stream with benzene toproduce a cumene product stream. The integrated system includes afluidized reactor zone wherein the hydrocarbon feedstock contacts acatalyst to produce a cracked effluent stream including propane andpropylene. The system also includes a separation zone for separating thecracked effluent stream into at least one separator liquid stream and aseparator vapor stream. The at least one separator liquid streamincludes C₃+ hydrocarbons; the separator vapor stream includes C₂−hydrocarbons. The system also includes stripper to remove C₂−hydrocarbons from the C₃+ hydrocarbon stream, a debutanizer to removeC₅+ hydrocarbons from the C₃+ hydrocarbon stream, a C₃/C₄ splitter toproduce a propane/propylene stream and various units upstream anddownstream of the C₃/C₄ splitter to remove impurities other than propaneand propylene. The combined propane/propylene stream is fed through aprocess line to an alkylation reactor for reacting at least some of thepropylene in the combined propane/propylene stream with benzene to formcumene.

Intercoolers used to cool the alkylation reactor can be used to supplyheat to a splitter column of the FCC process system. The bottoms streamfrom the cumene column can be used as an absorber solvent or can beadded to the cracked effluent stream at the main column of the FCCprocess.

Other advantages will be apparent to those skilled in the art from thefollowing detailed description taken in conjunction with the appendedclaims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic diagram of a system for catalyticcracking a heavy hydrocarbon feedstock and obtaining selectedhydrocarbon fractions, including light olefins via an absorption-basedproduct recovery;

FIG. 2 is a simplified schematic diagram of a system for convertingpropylene to cumene that is integrated with the system of FIG. 1; and

FIG. 3 is a simplified schematic diagram of another system forconverting propylene to cumene that is also integrated with the systemof FIG. 1.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 schematically illustrates a system 10 a for catalytic cracking aheavy hydrocarbon feedstock and obtaining light olefins viaabsorption-based product recovery and FIGS. 2 and 3 schematicallyillustrates related systems 10 b, 10 c for efficiently converting thelight olefins from the system 10 a into one or more usefulintermediates. Those skilled in the art and guided by the teachingsherein provided will recognize and appreciate that the illustratedsystems 10 a, 10 b, 10 c have been simplified by eliminating some usualor customary pieces of process equipment including some heat exchangers,process control systems, pumps, fractionation systems, and the like. Itmay also be discerned that the process flows depicted in FIGS. 1-3 maybe modified in many aspects without departing from the basic overallconcepts disclosed herein.

In the cracking system 10 a, a suitable heavy hydrocarbon feedstockstream is introduced via a line 12 into a fluidized reactor zone 14wherein the heavy hydrocarbon feedstock contacts a hydrocarbon crackingcatalyst zone to produce a hydrocarbon effluent comprising a range ofhydrocarbon products, including light olefins such as propylene andlight hydrocarbons such as propane.

Suitable fluidized catalytic cracking reactor zones for use in thepractice of such an embodiment may, as is described in above-identifiedU.S. Pat. No. 6,538,169, include a separator vessel, a regenerator, ablending vessel, and a vertical riser that provides a pneumaticconveyance zone in which conversion takes place. The arrangementcirculates catalyst and contacts the catalyst with the feed.

The FCC catalyst typically comprises two components that may or may notbe on the same matrix. The two components are circulated throughout thereactor 14. The first component may include any of the well-knowncatalysts that are used in the art of fluidized catalytic cracking, suchas an active amorphous clay-type catalyst and/or a high activity,crystalline molecular sieve. Molecular sieve catalysts are preferredover amorphous catalysts because of their much-improved selectivity todesired products. Zeolites are the most commonly used molecular sievesin FCC processes. Preferably, the first catalyst component comprises alarge pore zeolite, such as a Y-type zeolite, an active aluminamaterial, a binder material, comprising either silica or alumina and aninert filler such as kaolin.

The zeolitic molecular sieves appropriate for the first catalystcomponent should have a large average pore size. Typically, molecularsieves with a large pore size have pores with openings of greater than0.7 nm in effective diameter defined by greater than 10 and typically 12membered rings. Pore Size Indices of large pores are above about 31.Suitable large pore zeolite components include synthetic zeolites suchas X-type and Y-type zeolites, mordenite and faujasite. It has beenfound that Y zeolites with low rare earth content are preferred in thefirst catalyst component. Low rare earth content denotes less than orequal to about 10 wt % rare earth oxide on the zeolite portion of thecatalyst. Octacat™ catalyst made by W R. Grace & Co is a suitable lowrare earth Y-zeolite catalyst.

The second catalyst component comprises a catalyst containing, medium orsmaller pore zeolite catalyst exemplified by ZSM-5, ZSM-11, ZSM-12,ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other similar materials. U.S. Pat.No. 3,702,886 describes ZSM-5. Other suitable medium or smaller porezeolites include ferrierite, erionite, and ST-5, developed by Petoleosde Venezuela, S.A. The second catalyst component preferably dispersesthe medium or smaller pore zeolite on a matrix comprising a bindermaterial such as silica or alumina and an inert filer material such askaolin. The second component may also comprise some other activematerial such as Beta zeolite. These catalyst compositions have acrystalline zeolite content of 10-25 wt % or more and a matrix materialcontent of 75-90 wt %. Catalysts containing 25 wt % crystalline zeolitematerial are preferred. Catalysts with greater crystalline zeolitecontent may be used, provided they have satisfactory attritionresistance. Medium and smaller pole zeolites are characterized by havingan effective pole opening diameter of less than or equal to 0.7 nm,rings of 10 or fewer members and a Pore Size Index of less than 31.

The total catalyst composition should contain 1-10 wt % of a medium tosmall pore zeolite with greater than or equal to 1 75 wt % beingpreferred. When the second catalyst component contains 25 wt %crystalline zeolite, the composition contains 4-40 wt % of the secondcatalyst component with a preferred content of greater than or equal to7 wt %. ZSM-5 and ST-5 type zeolites are particularly preferred sincetheir high coke resistivity will tend to preserve active cracking sitesas the catalyst composition makes multiple passes through the riser,thereby maintaining overall activity. The first catalyst component willcomprise the balance of the catalyst composition. The relativeproportions of the first and second components in the catalystcomposition will not substantially vary throughout the FCC unit 14.

The high concentration of the medium or smaller pore zeolite in thesecond component of the catalyst composition improves selectivity tolight olefins by further cracking the lighter naphtha range molecules.But at the same time, the resulting smaller concentration of the firstcatalyst component still exhibits sufficient activity to maintainconversion of the heavier feed molecules to a reasonably high level.

The relatively heavier feeds suitable for processing in accordanceherewith include conventional FCC feedstocks or higher boiling orresidual feeds. A common conventional feedstock is vacuum gas oil whichis typically a hydrocarbon material prepared by vacuum fractionation ofatmospheric residue and which has a broad boiling range of from 315-622°C. (600-1150° F.) and, more typically, which has a narrower boilingpoint range of from 343-551° C. (650-1025° F.). Heavy or residual feeds,i.e., hydrocarbon fractions boiling above 499° C. (930° F.), are alsosuitable. The fluidized catalytic cracking processing the invention istypically best suited for feedstocks that are heavier than naptha rangehydrocarbons boiling above about 177° C. (350° F.).

The effluent or at least a selected portion thereof is passed from thefluidized reactor zone 14 through a line 16 into a hydrocarbonseparation system 20, which may include a main column section 22 and astaged compression section 24. The main column section 22 may desirablyinclude a main column separator and associated main column receiverwhere the fluidized reactor zone effluent can be separated into desiredfractions including a main column vapor stream that is passed throughline 26 to the two stage compressor 24, and a main column liquid stream,which is passed through line 30 to the absorber 40. Other fraction linessuch as including a heavy gasoline stream, a light cycle oil (“LCO”)stream, a heavy cycle oil (“HCO”) stream and a clarified oil (“CO”)stream, for example, may not be shown or specifically described.

The main column vapor stream line 26 is introduced into the stagedcompression section 24. The staged compression section 24 results in theformation of a high pressure separator liquid stream in a line 32 and ahigh pressure separator vapor stream in a line 34. While the pressure ofsuch high pressure liquid and high pressure vapor can vary, in practicesuch streams are typically at a pressure ranging from about 1375 kPag toabout 2100 kPag (about 200 psig to about 300 psig). The compressionsection 24 may also result in the formation of a stream of spill backmaterials largely composed of heavier hydrocarbon materials and such ascan be returned to the main column section 22 via the line 35.

The high pressure separator liquid stream 32 includes C₃+ hydrocarbonsand is substantially free of carbon dioxide and hydrogen sulfide. Thehigh pressure separator vapor stream 34 includes C₂− hydrocarbons andtypically includes some carbon dioxide and hydrogen sulfide.

The separator vapor stream line 34 is introduced into an absorption zone36, which includes the primary absorber 40, where the separator vaporstream 34 is contacted with a debutanized gasoline material provided bythe line 42 and the main column overhead liquid stream 30 to absorb C₃+materials and separate C₂ and lower boiling fractions from the separatorvapor stream. In general, the absorption zone 36 includes the primaryabsorber 40 that suitably includes a plurality of stages with at leastone and preferably two or more intercoolers interspaced therebetween toassist in achieving desired absorption. In practice, such a primaryabsorber 40 includes about five absorber stages between each pair ofintercoolers. The primary absorber 40 may include at least about 15 to25 ideal stages with 2 to 4 intercoolers appropriately spaced betweenthe stages.

C₃+ hydrocarbons absorbed in or by the debutanized gasoline stream 42and main column liquid stream 30 in the absorber 40 can be passed viathe line 43 back to the two-stage compressor 24 for further processing.The off gas from the primary absorber 40 passes via a line 44 to asecondary or sponge absorber 46. The secondary absorber 46 contacts theoff gas with light cycle oil from a line 50. Light cycle oil absorbsmost of the remaining C₄ and higher hydrocarbons and returns to the mainfractionators via a line 52. A stream of C₂− hydrocarbons is withdrawnas of gas from the secondary or sponge absorber 46 in the line 54 forfurther treatment as later described herein.

The high pressure liquid stream 32 from the compressor 24 is passedthrough to the stripper 62 which removes most of the C₂ and lightergases through the line 64 and passes them back to the compressor 24. Inpractice, the stripper 62 can be operated at a pressure ranging fromabout 1375 kPag to about 2100 kPag (about 200 psig to about 300 psig)with a C₂/C₃ molar ratio in the stripper bottoms of less than 0.001 andpreferably with a C₂/C₃ molar ratio in the stripper bottoms of less thanabout 0.0002 to about 0.0004.

As discussed in greater detail below, the reboiler heat exchanger 63 maybe driven by heat generated in the alkylation reactor 164 shown in FIGS.2-3. Specifically, one or more inter-coolers 63 a (FIGS. 2-3) may becombined with the reboiler heat exchanger 63 (FIG. 1).

As shown, the C₂ and lighter gases in the line 64 are combined in thecompressor 24 with the main column vapor stream 26 to form with highpressure separator vapor stream 34 that is fed into the primary absorber40. The stripper 62 supplies a liquid C₃+ stream 66 to the debutanizer70. A suitable debutanizer 70 includes a condenser (not shown) thatdesirably operates at a pressure ranging from about 965 kPag to about1105 kPag (about 140 psig to about 160 psig), with no more than about 5mol % C₅ hydrocarbons in the overhead and no more than about 5 mol % C₄hydrocarbons in the bottoms. More preferably, the relative amount of C₅hydrocarbons in the overhead is less than about 1-3 mol % and therelative amount of C₄ hydrocarbons in the bottoms is less than about 1-3mol %.

A stream of C₃ and C₄ hydrocarbons from the debutanizer 70 is taken asoverhead through line 72 for further treatment as described below andthe bottoms stream 76 from the debutanizer 70 comprises gasoline, partof which forms the stream 42 which is fed to the top of the primaryabsorber 40 where it serves as the primary first absorption solvent.Another portion of the stream of debutanized gasoline is passed throughthe line 77 to a naphtha splitter (not shown), which may be a dividingwall separation column.

The C₂− hydrocarbon stream 54 withdrawn from the secondary or spongeabsorber 46 is passed through a further compression section 90 to form acompressed vapor stream 92 that is passed into a compression ordischarge vessel 94. The discharge vessel 94 forms a liquid knockoutstream generally composed of heavy components (e.g., C₃+ hydrocarbonsthat liquefy in the discharge vessel 94) and are withdrawn in the line96. The discharge vessel 94 also forms an overhead vapor stream 100primarily comprising C₂− hydrocarbons, with typically no more than traceamounts (e.g., less than 1 wt %) of C₃+ hydrocarbons.

The overhead stream 100 is passed to an amine treatment section 102 toremove CO₂ and H₂S. The utilization of amine treatment system 102 forcarbon dioxide and/or hydrogen sulfide removal is well known in the art.Conventional such amine treatment systems typically employ an aminesolvent such as methyl diethanol amine (MDEA) to absorb or otherwiseseparate CO₂ and H₂S from hydrocarbon stream materials. A stripper orregenerator is typically subsequently used to strip the absorbed CO₂ andH₂S from the amine solvent, permitting the reuse of the amine solvent.

While such amine treatment has proven generally effective for removal ofcarbon dioxide from various hydrocarbon-containing streams, theapplication of such amine treatment to ethylene-rich hydrocarbon andcarbon dioxide-containing streams, such as being processed at this pointof the subject system, may experience some undesired complications assome of the olefin material may be co-absorbed with the CO₂ and H₂S inor by the amine solvent. Such co-absorption of olefin materialundesirably reduces the amounts of light olefins available for recoveryfrom such processing. Moreover, during such subsequent stripperprocessing of the amine solvent, the presence of such olefin materialscan lead to polymerization. Such polymerization can lead to degradationof the amine solvent and require expensive off-site reclamationprocessing.

It may be desirable to utilize an amine treatment system such asincludes or incorporates a pre-stripper interposed between the aminesystem absorber and the amine system stripper/regenerator. Such aninterposed pre-stripper, can desirably serve to separate hydrocarbonmaterials, including light olefins such as ethylene, from the carbondioxide and amine solvent prior to subsequent processing through theregenerator/stripper. A CO₂/H₂S outlet is shown at 103.

A stream 104 containing C₂− hydrocarbons substantially free of carbondioxide is passed to a dryer section 106 with a water outlet line 107. Astream containing dried C₂− hydrocarbons substantially free of carbondioxide is passed via a line 108 to an acetylene conversion section orunit 110. As is known in the art, acetylene conversion sections or unitsare effective to convert acetylene to form ethylene. Thus, anadditionally ethylene-enriched process stream 112 is withdrawn from theacetylene conversion section or unit 110 and passed to the optionaldryer 114 or to the CO₂, carbonyl sulfide (“COS”), arsine and/orphosphine treater 116 as is known in the art to effect removal of CO₂,COS, arsine and/or phosphine.

Water is withdrawn from the dryer 114 through the line 117. CO₂, COS,Arsine and/or Phosphine are withdrawn through the line 118, and thetreated stream 120 is introduced into a demethanizer 122. A suitabledemethanizer 122 may include a condenser (not specifically shown) thatdesirably operates at a temperature of no greater than about −90° C.(−130° F.), more preferably operates at a temperature in the range ofabout −90° C. to about −102° C., preferably about −96° C. (−130° toabout −150° F., preferably at about −140° F.) In addition, thedemethanizer 122 may operate with a methane to ethylene molar ratio inthe bottoms of no greater than about 0.0005 and, more preferably at amethane to ethylene molar ratio in the bottoms of no greater than about0.0003 to about 0.0002.

The overhead stream 124 of methane and hydrogen gas from thedemethanizer 122 may be used as a fuel or, if desired, taken for furtherprocessing or treatment such as to a pressure swing absorption unit (notshown) for H₂ recovery. The demethanizer outlet stream 126 is passed toa C₂/C₂=splitter 125, which produces an ethylene stream 123, a ethanestream 121 and a light ends overhead stream 119

Still referring to FIG. 1, the stream 72 containing C₃ and C₄hydrocarbons taken overhead from the debutanizer 70 may contain somesignificant relative amounts of hydrogen sulfide and is thereforepreferably passed to a sulfide removal treatment unit 128, such as anamine treatment section, where hydrogen sulfide is removed through theline 129 and the treated stream 130 is passed to an optional extractionunit 132 to catalytically oxidize mercaptans present to disulfides via acaustic wash, which are removed through the line 134.

The resulting stream 136 is passed to the C₃/C₄ splitter 138. A suitableC₃/C₄ splitter includes a condenser (not specifically shown) thatdesirably operates at a pressure in the range of about 1650 kPag toabout 1800 kPag (about 240 psig to about 260 psig), preferably at apressure of about 1724 kPa (about 250 psig) and desirably operates suchthat there is no more than about 5 mol % C₄s in the overhead productstream, preferably less than about 1 mol % C₄s in the overhead productstream and no mole than about 5 mol % C₃s in the bottoms stream,preferably less than about 1 mol % C₃s in the bottoms stream.

The C₃/C₄ splitter 138 forms a bottoms stream 140 of C₄+ hydrocarbonsfor use as either for product recovery or further desired processing, asis known in the art. The C₃/C₄ splitter 138 also forms a stream 142composed primarily of C₃ hydrocarbons.

The propylene/propane stream 142 may be passed to dryer 150 for theremoval of water through the line 152 before being passed on to aregenerative COS treater 154 to remove COS through the line 156 beforebeing passed through the arsine and/or phosphine treater 158 to effectremoval of trace amounts of arsine and/or phosphine through the line 160and producing an propane/propylene product stream 162.

Turning to FIG. 2, the combined propane/propylene stream 162 isintroduced at various stages to the to the alkylation reactor 164,without pre-heating and without separating the propane, where thepropylene reacts catalytically with benzene provided in the form offresh benzene through the line 166 and recycled benzene through the line168. Because propane is essentially inert to the cumene process system10 b, the need for an upstream propane/propylene splitter is notrequired. Further, pre-heating the cool propane/propylene stream 162from the arsine/phosphine treater 122 is not required. As the materialin the combined propane/propylene stream 162 is liquid, it may bedelivered at pressures ranging from about 2900 to about 4000 kPa (˜421to ˜580 psi) using a conventional pump 125.

Propylene in the stream 162 reacts with the benzene in the alkylationreactor 164 to produce a combined product stream 172 that will includecumene, DIPB, TIPB, propane, and unreacted ethylene and benzene. Thecombined alkylation product stream 172 is partially recycled back to thealkylation reactor 164 through the line 173 and also passed through theline 174 to the depropanizer column 175 where it is combined with thefresh benzene stream 166. Propane is taken as overhead through the line178 and benzene is recycled though the line 179. The bottoms product181, which includes some benzene as well as cumene, DIPB and TIPB, ispassed to the benzene column 182 where benzene is taken as the overheadstream 168 and the cumene, DIPB, TIPB and heavies in the bottoms stream183 is passed to the cumene column 184. Cumene is taken as the overheadstream and the DIPB, TIPB and heavies in the bottoms stream 187 ispassed to the DIPB/TIPB column 188. A DIPB/TIPB rich overhead stream isrouted to the tranalkylation reactor where it is combined with thebenzene recycle stream 194 to produce a reactor effluent stream 196 withcumene, DIPB, TIBP and benzene that is combined with the bottoms stream181 from the depropanizer 175 and passed to the benzene column 182. TheDIPB/TIPB column 188 also produces an overhead drag stream 198 and aheavies bottoms stream 199.

The intercooler(s) 63 a in the alkylation section 164 typically requiresa cooling water utility. In accordance with this disclosure, integratingthe alkylation intercooler(s) 63 a (FIG. 2) with the C₂− stripper 62(FIG. 1) reduces the need for additional heating by LP steam which wouldbe required by the reboiler 63 (FIG. 1). All or most of the heat for thereboiler 63 can be provided by the intercooler 63 a

An additional integration option is illustrated in FIG. 3 and involveseliminating the transalkylation section 192 and the DIPB/TIBP column188. The cumene column bottoms 187 is passed to the primary absorber 40(FIG. 1) by combining the cumene bottoms stream 187 with the debutanizedgasoline recycle stream 42 (FIG. 1) to supplement some of thedebutanized gasoline recycle, reducing the amount of recycle that isrequired. If all of the propylene produced by the FCC process 10 a isused in the cumene process 10 c, the cumene column bottoms 187 wouldreduce the required debutanized gasoline recycle stream 42 by an amountranging from about 15 to about 20%. The DIPB, TIBP and other heavieswould ultimately end up as a high octane component in the gasolineproduct stream 77. Because the cumene column bottoms 187 contains asmall fraction of heavy components (e.g., TIPB and heavies) that may beslightly too heavy for the gasoline product, another alternative shownin FIG. 3 is to send the cumene column bottoms 187 to the FCC maincolumn 22, where the heavier species in this stream would be removed ina heavier fraction such as the heavy naphtha draw. The lighter speciesin this stream will still act to reduce the required debutanizedgasoline recycle stream 42, as they will exit in the unstabilizedgasoline stream 77 that is recovered from the main column overheadstream 26.

Thus, improved processing schemes and arrangements are provided forobtaining propylene and propane via the catalytic cracking of a heavyhydrocarbon feedstock and converting the propylene into cumene withoutseparating the propane from the alkylation feed stream. Moreparticularly, processing schemes and arrangements are provided thatadvantageously eliminate the need to separate propylene from propaneproduced by a FCC process prior to using the combined propylene/propanestream as a feed for cumene alkylation process.

The disclosed processes and schemes may be practiced in the absence ofany element, part, step, component, or ingredient which is notspecifically disclosed herein.

1. An integrated process for catalytically cracking a heavy hydrocarbonfeedstock, obtaining a combined propane/propylene stream, and reactingthe propylene of the combined propane/propylene stream with benzene toproduce a cumene product stream, the integrated process comprising:contacting a heavy hydrocarbon feedstock with a hydrocarbon crackingcatalyst in a fluidized reactor zone to produce a hydrocarbon effluentstream comprising propane and propylene; separating the hydrocarboneffluent stream in a separation zone into a separator liquid stream anda separator vapor stream; stripping C₂− hydrocarbon materials from theseparator liquid stream in a stripper column to form a C₃+ hydrocarbonprocess stream substantially free of C₂− hydrocarbons; separating C₄+hydrocarbons and impurities from the C₃+ hydrocarbon process stream toprovide a combined propane/propylene stream; pumping the combinedpropane/propylene stream as a liquid at a pressure ranging from about2900 kPa to about 4000 kPa to an alkylation zone to an alkylation zone;reacting at least some of the propylene of the combinedpropane/propylene stream with benzene in the alkylation zone to producecumene; and heating the stripper column with at least one heat exchangerdriven by heat generated in an alkylation reactor of the alkylationzone.
 2. The process of claim 1 wherein propane is not stripped from thecombined propane/propylene stream prior to the combinedpropane/propylene stream entering the alkylation reactor.
 3. The processof claim 1 wherein the alkylation zone comprises an alkylation reactorthat comprises a plurality of catalyst beds and a plurality of feedinlets, and the process further comprises dividing the combinedpropane/propylene stream amongst the plurality of feed inlets.
 4. Theprocess of claim 1 wherein the alkylation zone produces a bottoms streamcomprising polyisopropyl benzenes (PIPBs) and heavies, the processfurther comprising: combining the bottoms stream comprising PIPBs andheavies with the hydrocarbon effluent stream upstream of the separationzone.
 5. The process of claim 1 wherein the alkylation zone produces abottoms stream comprising polyisopropyl benzenes (PIPBs) and heavies,the process further comprising: contacting the separator vapor streamwith an absorption solvent in an absorption zone that comprises thebottoms stream comprising PIPBs and heavies from the alkylation zone toseparate a C₂− stream from the separator vapor stream.
 6. The process ofclaim 1 wherein the combined propane/propylene stream additionallycomprises hydrogen sulfide and the process additionally comprises:contacting at least a portion of the combined propane/propylene streamwith an amine solvent to remove hydrogen sulfide therefrom.
 7. Theprocess of claim 1 wherein the combined propane/propylene streamadditionally comprises mercaptans and the process further comprises:catalytically oxidizing at least some mercaptans in the combinedpropane/propylene stream.
 8. The process of claim 1 wherein the C₄+hydrocarbons are separated from the C₃+ hydrocarbon process stream in aC₃/C₄ splitter.
 9. The process of claim 1 wherein the combinedpropane/propylene stream is passed through one or more of a dryer, a COStreater, an arsine treater and a phosphine treater prior to the combinedpropane/propylene stream being passed to the alkylation zone.
 10. Anintegrated process for catalytically cracking a hydrocarbon feedstock,obtaining a combined propane/propylene stream, and reacting thepropylene of the combined propane/propylene stream with benzene toproduce a cumene product stream, the integrated process comprising:contacting a heavy hydrocarbon feedstock with a hydrocarbon crackingcatalyst in a fluidized reactor zone to produce a hydrocarbon effluentstream comprising propane and propylene; separating the hydrocarboneffluent stream in a separation zone into a separator liquid streamcomprising propane and propylene and a separator vapor stream; strippingC₂− hydrocarbon materials from the separator liquid stream in a strippercolumn to form a combined propane/propylene stream substantially free ofC₂− hydrocarbons; pumping the combined propane/propylene stream as aliquid at a pressure ranging from about 2900 kPa to about 4000 kPa to analkylation reactor and exothermically reacting at least some of thepropylene in the combined propane/propylene stream with benzene in thealkylation reactor to produce a cumene stream, heat and a polyisopropylbenzenes (PIPBs) stream; heating the stripper column with heat from thealkylation reactor.
 11. The process of claim 10 wherein propane is notstripped from the combined propane/propylene stream prior to thecombined propane/propylene stream entering the alkylation reactor. 12.The process of claim 10 further comprising combining the PIPBs streamwith the hydrocarbon effluent stream upstream of the separation zone.13. The process of claim 10 the process further comprising: contactingthe separator vapor stream with an absorption solvent in an absorptionzone that comprises the PIPBs stream from the alkylation zone toseparate a C₂− stream from the separator vapor stream.